Deposition of organic and inorganic semiconductor structures needs as homogeneous temperature distribution as possible. Variations of the processing temperature of some degree across, for example, a semiconductor wafer changes the growth conditions and thus the characteristics of the grown semiconductor layer. An example is the growth of LEDs emitting visible light on the basis of GaN. The growth temperature above 1000° C. has to be maintained within 0.5° C. in order to avoid wavelength shifts of the LEDs which in consequence require costly binning of products.
U.S. Pat. No. 8,222,574 B2 discloses, for example, an apparatus and a corresponding method for achieving uniform heating or cooling of a substrate during a rapid thermal process. The apparatus includes a thermal mass or plate adjacent to an edge ring to heat or cool the edge ring for controlling the temperature of the edge ring. Heat sources like laser diodes may be used to heat the edge ring and/or the substrate. The reliability and homogeneity of the heating process of the apparatus is still unsatisfactorily.
US 2010/0038833 A1 discloses an annealing apparatus comprising a multitude of LEDs, which is free from a problem of reduced light energy efficiency resulted by the reduction of light emission amount due to a heat generation and capable of maintaining stable performance.